48 C? Summer is the wrong time to grow tomatoes in your area.

If you can keep your plants from drying out completely and give them some shade during the hottest part of the day, they may survive and grow leaves and stems, but their flowers will just fall off without making any fruit at those temperatures.

There are some heat-tolerant tomatoes that cope with higher temperatures a little better, but, for the most part, you want to time things so that your plants are blooming when daytime temperatures are not much higher than 32 C and nighttime temperatures are not higher than 24 C. This is when the flowers will pollinate well and your tomatoes will make fruit.

Perhaps this forum will be helpful to you: https://gardeningpakistan.com/

I think people there will be more familiar with your specific area and the climate (I assume Pakistan has varying climates in different areas and altitudes) and be able to help you figure out when to start your tomato plants from seeds and when to plant them outside.

Here is a post from there about tomatoes: https://gardeningpakistan.com/viewtopic.php?f=31&t=795

We can probably be helpful with all kinds of questions about growing methods, pests and disease, etc., but I don't think we have many members here who will be familiar with the specific challenges of your climate.

Agree that you are likely trying to grow them at the wrong time of year for your location. According to the Pakistani Gardening forum you should be planting in January for the summer crop or Sept for a Fall crop. A June-July planting can only work in certain parts of the country apparently.

https://gardeningpakistan.com/viewtopic.php?f=31&t=795

Dave

I agree with others that the ideal time to plant is before it gets that hot (or after, depending on your season). However, that doesn't mean you can't grow stuff now. There's usually a way to do a thing if you're determined enough.

From my experience during a year where it got up to 116 to 118° F. one day (and pretty hot other days, for a long time), I wouldn't even bother trying to start tomatoes indoors, unless you have a great temperature control system indoors that can simulate the temperatures you need (not just daytime temperatures, but night temperatures, too). You could try starting them under lights in a cool root cellar. Or, you could try outdoors. Your indoor temperatures are probably pretty warm, and consistently pretty warm, whereas outdoor temperatures are very hot, and, I'm guessing much cooler at night than in the day. There may be a chance that your nights are cool enough to allow tomatoes to sprout (I wouldn't count on it, but you can experiment). The difference in temperatures between day and night can make a difference for tomatoes. However, if watered soil doesn't even grow weeds, I would worry. I would not try sprouting tomatoes in a container in those temperatures. The container will be too hot and dry out too fast. The ground will be cooler, I think. Your soil-type may matter a lot, too. I would be more comfortable with a soil that insulates well, at those temperatures, like maybe clay (a good clay that actually absorbs water instead of letting it pool on top and evaporate; partial clay or clay loam may work). Such soil may or may not be the best for germination even at good temperatures (so, you may need to plant a fair amount of seeds).

Now, I have an idea. You can dig a hole deep enough that it's cooler down there, and plant seeds in it. One of the drawbacks to planting tomatoes too deep (I tried planting extra-long tomatoes 5-feet deep in our clay-type soil one year) seems to be that the roots get too cold or something, and this seems to slow the growth (although they still grow). So, that might be one way to regulate temperatures and light levels. You might want to dig a very deep hole, wait a day or two, and then measure the temperature at various depths. Then you'll know how deep to dig your hole to get the right temperature for tomatoes. Open holes seem able to stay pretty cool even in high temperatures (at least with compact soil like ours). However, with the moisture and closeness of the soil, I might be concerned that fungi might have an advantage there, but I'd probably try it, at least. If you have clay down below, you'll want a tomato variety that does well in clay (some of them do a lot better than others; Amana Orange grows extra-vigorously in clay-type soil in my experience, but some varieties don't grow much at all). You'll want to make sure your hole is a good shape to allow for proper watering. If the hole is not a good shape, and you amend the soil to make it looser or such, the water may make your soil float or such, and cause distress. Amending the soil too much to make it loose may also cause the tomato not to venture out into the unamended soil, if it's compact (so, I would make sure it's not *too* different in how compact it is). If your hole is too wide, or if it's not deep enough, it may be too hot, still, but if it's too narrow and deep, you may not have enough light, or it may be too cold.
You might try rooting cuttings instead of growing from seed, if you have a friend with tomato plants who likes to prune suckers. That may be easier to do in the heat than sprouting seeds.

When your tomatoes actually start to grow, you may want to shower them. In my area, that helps them to grow faster, and they seem to do better when it's hot and dry. I think the water pressure on the plants has as much to do with it as the actual wetness factor, though. It probably helps the plants to develop better, stronger roots (like wind does), and the water splattering against the leaves may help to activate the plants' defenses against insects and disease (touching them is supposed to do that, which is one reason why I think this may be true). I did notice that insects left my tomatoes and peppers alone almost entirely when I did this. If you want the benefits of showered tomatoes while they're still younger, grow a whole bunch of seeds, and don't thin them until they're big enough to be showered on their own. The plants will support each other when you shower them. When they're big enough, thin to one plant with scissors (don't pull them up by the roots). You actually need to use a shower nozzle, though (don't just spray your plants with a hose; that doesn't work, in my experience; plus, it knocks the plants over and gets a lot more soil all over them).

Of course, water and soil on leaves is said to contribute to fungal diseases, but it doesn't seem to be as bad of an issue in semi-arid to arid areas.

Potassium can help plants be a little more heat-tolerant. I like potassium sulfate, personally (and/or wood ash). Too much potassium can slow the growth of your plants, though (or make them not grow as big).

You may try oxheart tomatoes with sparse foliage. They have smaller leaves; so, in theory, they should absorb less sunlight and be less bothered by it (although maybe sun scald might be an issue for your fruits). However, you'll want to make sure they're adapted to your area (and because oxhearts are grown heavily in more ideal conditions, it may not be easy). Saving your seeds and growing them again every year for a few years should help to acclimatize your varieties to your climate and soil better. I've found that to be true with at least some kinds of plants. I think it probably takes about 3 to 8 years of seed-saving to fully acclimatize a variety (from my observations of reseeding flowers and how they've done year after year), but you can potentially notice a big difference after a single year.